public function testOnlyNumericArraysAreCastableAsAGraphList()
 {
     $shouldPassOne = GraphObjectFactory::isCastableAsGraphList([]);
     $shouldPassTwo = GraphObjectFactory::isCastableAsGraphList(['foo', 'bar']);
     $shouldFail = GraphObjectFactory::isCastableAsGraphList(['faz' => 'baz']);
     $this->assertTrue($shouldPassOne, 'Expected the given array to be castable as a GraphList.');
     $this->assertTrue($shouldPassTwo, 'Expected the given array to be castable as a GraphList.');
     $this->assertFalse($shouldFail, 'Expected the given array to not be castable as a GraphList.');
 }